1. FIELD OF THE INVENTION
This invention relates to an amplifier circuit and more particularly to a complementary metal-insulator-semiconductor (C-MIS) amplifier circuit comprising a p-channel metal-insulator-semiconductor field effect transistor (referred to as MIS FET or simply as FET, hereinbelow) and an n-channel MIS FET.
2. DESCRIPTION OF THE PRIOR ART
Conventionally, such a circuit as shown in FIG. 4 has been known as a crystal oscillator circuit used in an electronic wristwatch from U.S. Pat. No. 3,676,801 issued to F. H. Musa, an American publication, "RCA COS/MOS Integrated Circuits Manual" by RCA Corporation, pages 192 to 205, 1972, etc. The circuit of FIG. 4 basically comprises a C-MIS inverter circuit including an n-channel FET M.sub.n and a p-channel FET M.sub.p, and a positive feedback circuit or a regenerative feedback loop connected between the input and output terminals of the inverter circuit and including a crystal oscillator X and capacitors C.sub.D and C.sub.G. A resistor R.sub.D provided at the output of the amplifier circuit serves to stabilize the oscillation frequency.
Such a circuit as described above, however, has a problem in that the power consumption becomes large. This can be described as follows.
When the complementary inverter amplifier circuit constituting the main part of the oscillator circuit is driven with a completely digital input signal without other components, the period during which both complementary FETs are turned on is very short and the power consumption due to the dc current passing through the two FETs caused little problem since the complementary FETs operate in a push-pull manner. When a linear (e.g., a sinusoidal) signal as shown in FIG. 5 is applied to the input terminal, however, the period during which the two FETs operate in the transfer region or in the neighborhood of the switching point (the region between the threshold voltages V.sub.thn and V.sub.thp of the FETs M.sub.n and M.sub.p, i.e., the hatched region Y in FIG. 5) becomes long and the power dissipation increases.